# Is a /48 still the smallest thing you can route independently?

• Subject: Is a /48 still the smallest thing you can route independently?
• From: mysidia at gmail.com (Jimmy Hess)
• Date: Thu, 11 Oct 2012 18:11:50 -0500
• References: <[email protected]> <[email protected]> <CAP-guGVB6FbxYcZFJ2EzKyue3rZ=by=ttZHodtwQ3yDHOKC1vA@mail.gmail.com>

```On 10/11/12, William Herrin <bill at herrin.us> wrote:
> On Thu, Oct 11, 2012 at 6:06 PM, Randy Carpenter <rcarpen at network1.net>
> wrote: >> How many sites do you have? If less than 192, /44 is
>> perfect, unless some of those sites require more than
>> a /48. Then, it gets more complicated :-)
>
> We're having a general math breakdown today. First Jeroen wants to fit
> 5 /48's in a /47 and now you want to fit 192 /48's in a /44.
> 48-44=4. 2^4=16.

Right,   last I checked  the smallest integer  >=   Log base 2 of  5
is  not less than or equal to 1,  therefore, you will never fit  5
/48s  in the network  just by  subtracting  1  from the prefix length.

if  you  want a  prefix /yy  that will accommodate a certain number
N  of   /xx

Then  you must ensure that
2^(xx - yy)   >=  N

not
5^(xx -yy )   >=  N

>
> -Bill
--
-J

```